According to the official Nokia exam prep documentation for classful routing logic (mirrored in the Nokia
4A0#101 study guide), routers R1, R2, and R3 run a classful routing protocol. When R1 advertises its directly connected subnets 10.1.1.0/24 and 10.1.2.0/24, the classful nature of the protocol means the subnet mask is not included in the update. The entire classful network portion is advertised instead. Since both your /24s fall within the same Class A network (10.0.0.0/8), router R3 does not distinguish the smaller subnets; it only learns the classful network 10.0.0.0/8.
From the guide:
"Routers R1, R2, and R3 are running a classful routing protocol. Router R1 advertises the directly connected networks 10.1.1.0/24 and 10.1.2.0/24. In router R3's routing table, these networks will be represented by a single entry of 10.0.0.0/8."